Typically, a solenoid valve comprises an armature movable between a first and second position for causing a needle valve to contact and separate from a valve seat. The extremes of these first and second positions are often defined by mechanical stops. Armatures can be moved in one direction by an electro-magnetic force generated by a coil of wire and moved in the opposite direction by a return spring. When the armature needle impacts a stop, the fuel injector bounces.
In high speed fluid metering solenoids, needle bounce is a problem because each bounce of the needle meters a small uncontrolled amount of fuel into the engine, to the detriment of emissions. As can be appreciated, the leakage of fuel into the engine will result in very unfavorable fuel economy. At either end of its motion, the armature has kinetic energy as a result of its mass and velocity. With no means for dissipating that energy, it is returned to the armature by the elastic collision with the stop. Eventually, the energy is dissipated after a series of collisions and bounces. The bounce of the armature and needle affects the operation of a fuel injector by prolonging or shortening the duration of injection, causing excessive wear in the valve seat area. This bounce causes increased injection time and quantity, reduced precision of fuel quantity delivery, and poor atomization.
It is seen then that there exists a need for a means of controlling the bounce of an armature needle, thereby diminishing the amount of fuel into the engine and the wear in the valve seat area.